The afforementioned track is in fact the reminents of the original Eastern Route. According to Robert Lindsell's The Rail Lines of Northern New England, in section 30 entitled, "Eastern Route", "a spur known as the Saco Industrial Branch was retained from Alfred Road (now US Route 111) through the former Eastern sation to serve several freight customers in Biddeford" (pg.156). All of this seemingly happened around 1944 when B&M abandoned south from Rigby Yard to 1.5 miles north of Saco (pg.154). As for the frequency of its current use I am not sure. Hopefully this insight helps eleviate any confusion!